Go to Admin > Add users, reset passwords, and more > Groups. For each group, choose Edit
, and select either a different custom domain name or the yourcompanyname.partner.onmschina.cn address.

For all other plans:

Go to Admin > Exchange > Recipients > Groups.

For each group that uses the custom domain in the email address, choose Edit
, and change the SMTP address and any custom address types to use either a different custom domain name or the yourcompanyname.partner.onmschina.cn address.

Choose SharePoint, and select the checkbox next to your public website.

If you want to keep your public website, choose Website domains, and in the New URL box, select either a different custom domain name or the yourcompanyname-public.sharepoint.cn address. Or, if you want to delete the contents of the public website, choose Delete.

Custom DNS records for the domain

If Office 365 manages your DNS records, and if you have added any custom DNS records to Office 365, remove them.